Many computer manufacturers are or will be using a printed circuit card or board which is attached to a larger printed circuit card or board and which in turn is connected to the electronics, particularly a buss or a Micro Channel, of the computer. The printed circuit card which has been added or piggy-backed is called a common mezzanine card. The common mezzanine card allows one or more functions such as a printer control, fax or network operation to be provided by the combined printed circuit card assembly without changing the electronic design of the host card to which the mezzanine card is attached. The mezzanine circuit card attached both physically and electrically to the host card permits, among other things, the external interfacing of the function provided. For example, if a function is that of printer control, the interface must accept a printer cable connector; while if the function is facsimile, of necessity, the interface must accept a standard telephone jack connector.
The Institute of Electrical and Electronic Engineers (IEEE) is an organization which establishes and administers some standards in the computer industry. A Draft Standard for a Common Mezzanine Card Family: CMC, P1386/Draft 2.0, Apr. 4, 1995, has been prepared by IEEE which will standardize the dimensional parameters and shape of a common mezzanine card bezel. However, the IEEE proposed standard is ambiguous as to the technique for mounting or attaching the mezzanine card bezel to the interface port or slot, also known as the expansion slot, within the frame of the computer or work station.
Several requirements must be satisfied in the attachment or mounting of the mezzanine card to the computer frame or work station frame. One such requirement is that the interface must be exposed so that the appropriate cables and connectors may be attached to the common mezzanine card at the interface.
A second requirement for the attachment or mounting of the mezzanine card is that electromagnetic radiation (EMR) generated within the computer frame must be suppressed, contained and prevented from escaping from the computer or work station unit and causing electromagnetic interference (EMI) either to the host device or to other electronic devices in the immediate area.
A third requirement for the attachment or mounting of the mezzanine card is that the interface structure of the mezzanine card be rigid and fixed relative to both the mezzanine card and the computer/work station frame to permit plugging and unplugging of cables without disturbing the position or the connection of the mezzanine card relative to other electronic circuits within the computer or work station.
Expansion cards previously have been provided with mounting brackets that are specifically designed to include the appropriate interface connector and thus not be universal. Additionally, present expansion cards require mounting brackets that are unique to a particular expansion card. Further, the expansion card brackets have relied only on a single screw to insure a grounding contact with the grounding circuit of the computer frame. Both of these design aspects provide less than desirable approaches in high performance computers because the bracket must be designed separately for each input/output interface requirement and the electromagnetic interference shielding is less than optimum in effectiveness for high speed computer operations.